Diaphragm and method of making such diaphragms



H. C. EGERTON.

DIAPHRAGM AND METHOD OF MAKING SUCH DIAPHRAGMS.

APPLICATION FILED JAN.4, 1918.

1,393,515 Patented Oct. 11, 1921..

Method of Making entree stares PATENT @FFHQE.

HENRY C. EGEBTON, OF PASSAIC, NEW JERSEY,

ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

DIAPHRAGM AND METHOD OF MAKING SUCH DIAPHRAGMS.

' Application filed January 4, 1918.

To a]! whom it may concern:

Be it known that I, HENRY C. EGERTON, a citizen of the United States, residing at Passaic, in the county of Passaic, State of New Jersey, have invented certain new and useful Improvements in Diaphragms and Such Diaphragms, of which the following is a full, clear, concise, and exact description.

This invention relates to vibratory diaphragms and methods of making the same A and more particularly to diaphragms for use in sound receiving and transmitting apparatus. I

The object of the invention is to provide a diaphragm which will respond effectively to sound vibrations, which'will be extremely durable, and in which moisture and temperature changes will be reduced to a minimum. In accordance with this object one feature of theinvention resides in providing a diaphragm comprising a plurality of layers of fabric so intimately associated through the medium of a phenolic condensation product as to produce a unitary diaphragm of homogeneous character throughout. Another feature resides in the method by which such a diaphragm is produced, and in accordance with this feature a plurality of layers of fibrous material are impregnated with a phenolic condensation product. and allowed to .dry, after which they are then united to form a unitary structure through the application of heat and pressure.

This invention may be better understood from the following description when considered in connection with the accompanying drawings illustrating embodiments thereof, and wherein; Figure 1 represents on an enlarged scale the separate layers of fabric assembled during the production of the diaphragm; Fig.2 is a View in cross section along the diameter of a completed diaphragm; Fig. 3 is arsimilar view .of a modified form of a completed diaphragm; Fig. 4 is a plan of a completed diaphragm; and Fig. 5 is a detailed view of three ad jacent layers illustrating the preferred arrangement of the threads of one layer transverse to the threads of adjacent layers.

The diaphragm comprises a plurality of layers of fabric disks, all of which may be of uniform diameter but which preferably have one or more disks such as 1 and 2 of Specification of Letters Patent.

Patented @ct. ii, rear.

Serial No. 210,260.

greater diameter than the remaining disks 3 and 4. The disks as shown are concentrically mounted so that the diaphragm when completed is thinner near the periphery than at the central portion. This renders the diaphragm relatively flexible at the periphery while relatively rigid at the central portion. If desired,'the increase in thickness of the diaphragm and the central portion may be made more gradual by having certain disks 4 of a diameter intermediate the diameters of the disks 1 and 3.

In the production of the diaphragm fibrous material such as linen, silk, cotton or paper is used for the disks; fine linen having been found especially desirable due to its texture and its ability to absorb the phenothalic condensation product used in the impregnation of the fibrous disks.

The first step in the manufacture of the diaphragm consists in thoroughly impregnating the sheets of fibrous material with a varnish of a phenolic condensation product and allowing such a sheet to dry thoroughly, after which disks of the desired size are cut from such sheets. If desired,the disks may be impregnated after cutting from the fibrous sheets but the former method is preferred.

After determining the size and relative thickness desired for any particular diaphragm the proper number and sizes of disks to produce such a diaphragm are selected and concentrically assembled one upon the other and if the diaphragm is to utilize two or more disks of the larger diameter these disks such erably positioned at the top and bottom of the pile as shown in Fig. 1.

To facilitate assembly an opening may be provided at the center ofeach disk designed to fit over a small pin or metallic rivet 5, and after assembly, if a rivet be used, a washer 6 would be put in place and the rivet headed down thereon to clamp the disk firmly together at the center.

In the assembly of a diaphragm formed of as 1 and 2 are prefdisks of woven fibrous material the disks place directly in a mold if desired, but if separately assembled, the assembled disks may now be placed between dies of a suitable mold and the dies brought together to force the disks into intimate association and to conform them to the mold. To produce a completed diaphragm, such as is shown in either Fig. 2 or Fig. 3 each die should be provided with concentric ridges mating with corresponding concentric depressions on the other die. producing in the completed diaphragm corresponding ridges 8 and depressions 9 which add to the rigidity of the central portion. The mold with the assembled disks'is then heated While under pressure to such adegree and for such a length of time that the separate disks are coalesced to form a homogeneous and unitary mass, and this mass is subsequently baked to produce a diaphragm which is hard and impervious to moisture.

In this step of the process the heating first softens the varnish with which the 'disks are impregnated so that under the pressure within the mold. it is forced into the interstices of the fibrous material. It is also forced into and absorbed by the fibers themselves and also thoroughly coats the exterior of the diaphragm. Further heating hardens the varnish and fibrous material whereby there results adiaphragm unaffected by moisture and which remains unchanged under temperatures encountered by apparatus employing diapbragms of this general character. It also results in a diaphragm in which a relatively rigid center may be obtained at the same time enabling the relative mass of the entire diaphragm and especially the central portion to be made very small.

In using diaphragms with certain classes of apparatus, such as in phonographic, recording and reproducing apparatus, it is quite customary to connect a movable member to the center of the diaphragm by a metallic rod or the like and the diaphragm construction shown in Fig. 2 is especially useful in this connection, inasmuch as the metallic rivet and washer enable a rod to be soldered directly thereto or the connection of the rod thereto by threading a portion of the stem to carry a nut and washer on both sides of the diaphragm, the rivet and washer 6 serving in either case to prevent injury to the diaphragm in the attachmentof such a rod thereto.

What is claimed:

1. A diaphragm composed of a phenolic condensation product reinforced with three or more superposed layers of woven fibrous material of two or more different areas, the two outer layers being of area substantially coextensive with the area of the diaphragm as a whole and inclosing one or more layers of smaller area, the interst ces of said woven fibrous material being impregnated with said phenolic condensation product. the whole diaphragm forming a substantially homogencous unit wherein the layers of woven,

fabric and the phenolic condensation product are intimately united.

2. A diaphragm composed of a phenolic condensation product reinforced with three or more layers of woven fibrous material superposed one upon the other, the outer layers being of area substantially coextensive with the area of the diaphragm as a whole and inclosing one or more layers of smaller said diaphragm being thicker at its center than at its edge. decreasing in thickness from center to edge by one or more steps and one or more concentric corrugations in said diaphragm. the whole diaphragm forming a substantially homogeneous unit, wherein the layers of woven fabric and the phenolic condensation product are intimately united.

4. A diaphragm composed of a phenolic condensation product reinforced with three of more superposed layers of woven fibrous material of two or more areas arranged so that both the warp and the weft threads of each layer extend transversely to the corresponding threads of the layer or layers next adjacent thereto. the'two outer layers being of area substantially co-extensive with the area of the diaphragm as a whole, and inclosing one or more layers of similar area, the interstices of said woven fibrous material being impregnated with said phenolic condensation product, the whole diaphragm forming a substantial homogeneous unit wherein the layers of woven fabric and the phenolic condensation product are intimately united.

In witness whereof, I hereunto subscribe my7name this 29th day of December, A. D., 191

HENRY C. EGERTON. 

